1. Field of the Invention
The present invention relates to a pyrrolo[1,2-a]pyrimidine compound that is useful as a coupler of a photographic material, a heat-sensitive recording material and the like, and to a heat-sensitive recording material that contains as color forming components the pyrrolo[1,2-a]pyrimidine compound serving as a coupler and a diazonium salt compound.
2. Description of the Related Art
With the recent advancement in performance of heat-sensitive recording materials, it has been strongly required to develop a heat-sensitive recording material that has cyan-color forming property and shows excellent hue, density of the formed color, and the like, in which shelf life, storability of images, image fixing property and the like are improved.
Diazonium salt compounds are compounds that have very high chemical activity and react with compounds called couplers (e.g., phenol derivatives, compounds having an active methylene group) to form an azo dye easily. Diazonium salt compounds are also light-sensitive and lose their activity when decomposed due to irradiation of light. Therefore, diazonium salt compounds have been used as light recording materials such as those used for diazo copies (see, "Shashin Kogaku no Kiso, Higin-en Shashin Hen (Fundamentals of Photographic Engineering, Edition of Non-Silver Salt Photography)" edited by Nippon Shashin Gakkai (Japan Photographic Association), Corona Co., Ltd. (1982), pp. 89 through 117, and pp. 182 through 201).
Further, by utilizing the property of diazonium salt compounds that they lose their activity due to decomposition by light, diazonium salt compounds have recently been used in recording materials that require fixing of images. As a representative example, there has been proposed a heat-sensitive recording material of a light fixing type in which a diazonium salt compound and a coupler are heated in accordance with image signals and react to form images, and thereafter, the images are fixed by irradiation of light (Hirotsugu Sato et al., "Gazo Denshi Gakkai Shi (Journal of the Image Electronics Society)", Vol. 11, No. 4 (1982), pp. 290-296, etc.).
However, the above-described recording materials using as a color forming element a diazonium salt compound have a drawback in that the activity of the diazonium salt compound is extremely high, and even in dark places, the diazonium salt compound thermally decomposes gradually such that the reactivity thereof is lost, and therefore, its shelf life as a recording material is short.
As one means for improving the above drawback, a method is known in which a diazonium salt compound is encapsulated in microcapsules. It has become possible by the above method to isolate the diazonium salt compound from substances promoting decomposition such as water, bases and the like, and to greatly improve the shelf life as a recording material (Tomomasa Usami et al., "Denshi Shashin Gakkai Shi (Journal of the Electrophotographic Association)", Vol. 26, No. 2, (1987), pp. 115 through 125). When the microcapsule is a microcapsule having a wall that has a glass transition temperature and in which the glass transition temperature is somewhat higher than room temperature such as urea resin and urethane resin, the capsule is called a heat-responsive microcapsule and is useful as a heat-sensitive recording material since, at room temperature, capsule walls exhibit non-permeability with respect to substances and, at the glass transition temperature or higher, exhibits permeability with respect to substances. In other words, if a heat-sensitive recording layer, which comprises heat-responsive microcapsules containing a diazonium salt compound, a coupler and a base, is applied onto a substrate to form a recording material, the diazonium salt compound can be kept stable for a long period of time, a color-formed image can be easily formed by heating, and further, the image can be fixed by irradiation of light.
As described above, it has become possible to greatly improve the stability of a diazonium salt compound by encapsulating the compound in microcapsules.
On the other hand, it is known that when 2-hydroxy-3-naphtoic anilides are used as couplers, they are excellent as color forming materials for heat-sensitive recording, and if a coupling reaction is effected with a 4-substituted amino-2-alkoxybenzene diazonium salt compound, a blue dye can be formed (Japanese Patent Application Laid-Open (JP-A) No. 2-225082).
However, the diazonium salt compound has a drawback in that, when a diazonium salt compound having .lambda..sub.max at a longer wavelength side is used, storability before use (background coloring property during storage before copying) of the recording material deteriorates. Further, in the case of a diazonium salt compound having .lambda..sub.max at a shorter wavelength side, when the aforementioned 2-hydroxy-3-naphtoic anilides are used, there are drawbacks in that the fixing property of images when irradiated with light is hindered, the hue extends over a long wavelength even to cyan, and further, storability of color-formed images (light fastness) is not sufficient.
As described above, there has not been obtained until now a heat-sensitive recording material that not only has a cyan color forming property but also provides excellent hue and sufficient density of the formed color, which results in satisfactory shelf life, image storability and image fixing property.